When it is desired to pull more than one trailer with a single truck tractor it is necessary to connect the second trailer to the rear of the first trailer. For this purpose a converter dolly is used which comprises wheels on a frame. A fifth wheel plate is carried on top of the frame for connection to the second trailer. A tongue member connects the frame to a pintle hitch on the rear of the first trailer. In this manner the converter dolly converts the second trailer from one having wheels only at the rear into a trailer having wheels both at the rear and at the front so that it may be towed behind another trailer.
The converter dolly has a single axle, with two large wheels on each end thereof. The frame and the tongue are made of heavy steel so as to be capable of withstanding the forces involved with the towing of a heavy trailer.
Since the converter dolly may weigh as much as 3000 pounds or so, it is difficult to move around a trailer yard, particularly when there are snow, ice, mud, sand, inclines, rocks, etc. in the trailer yard. Yet, it is frequently necessary to move the dolly around, e.g., between different trailers or to ready a trailer for connection directly to a truck tractor, or to ready a trailer for connection to another trailer. This is a very awkward, difficult, and hazardous task to be conducted manually. Frequently workers are injured when moving a dolly; for example, they may injure their back, pull muscles, etc.
Although it is possible to mount a hitch onto the front bumper of a tractor for the purpose of towing a dolly, this technique has not been totally satisfactory because of potential damage to the radiator of the tractor if the driver is careless when approaching the tongue of the dolly. It is not economical for a special vehicle to be designed just for the purpose of moving converter dollys in a trailer yard.
There has not heretofore been provided safe, effective and economical means for movement of converter dollys in a trailer yard.